Magaldrate is a substance deriving from the combination of aluminium hydroxide and magnesium hydroxide, corresponding to the formula Al5 Mg10 (OH)31 (SO4)2×H2O, with a molecular weight of approx. 1097. Magaldrate is described as a white, crystalline powder insoluble in water and alcohol; the dry base contains 34-46% magnesium oxide, 21-30% aluminium oxide and 13.3-17.5% sulphur trioxide.
Magaldrate is described in the official monographs of the European Pharmacopoeia (5th edition) and the US Pharmacopoeia (USP 29th edition).
Magaldrate is known and widely used as an ulcer treatment drug, as it possesses marked activity as an antacid buffer. It has been demonstrated that magaldrate has a rapid, persistent ability to maintain the gastric pH in a range of 3-5, and possesses cytoprotective activity. Its efficacy in promoting the healing of gastric and duodenal ulcers is well documented; basically, magaldrate neutralises the gastric acids by inhibiting the proteolytic activity of pepsin. The most recent studies demonstrate that antacids play a more important therapeutic role than as mere palliatives in the treatment of gastric ulcers. Another considerable advantage in the use of magaldrate is its excellent tolerability, demonstrated during its use in gastric disorders: in toxicity tests relating to single and repeated oral doses, it proved almost non-toxic.
Antacid compounds which exert a neutralising effect (US2003157195) or a buffer effect (U.S. Pat. No. 5,362,488 and U.S. Pat. No. 5,436,007) on damaged skin have been described.
Magaldrate not only acts as a pH buffer but possesses cytoprotective activity; published studies demonstrate that this activity is due to protection of the mucosa from lipid peroxidation and the ability to stimulate endogenous prostaglandin (PGE2) synthesis (Indian J. Physiol Pharmacol. 2000 July; 44(3):350-4 Arzneimittelforschung. 1989 July; 39(7):786-9); Hepato-Gastroenterology 1998; 45:2443-2446).
Evidence in favour of the cytoprotective activity of magaldrate has been obtained in laboratory animals and in tests on humans; it also possesses a marked ability to adsorb lysolecithin and bile acids, and consequently to prevent the epithelial damage to the gastric mucosa caused by those components.
Basically, Magaldrate creates an environment which promotes epithelial repair and cell regrowth.
Studies conducted on humans demonstrate that oral magaldrate intake is not followed by any significant absorption of aluminium or magnesium, and does not alter the calcium or phosphorus metabolism. Magaldrate only performs its action at gastrointestinal level, and has no systemic pharmacological effects or toxicity.
The therapeutic properties of magaldrate are not the same as those of other compounds based on aluminium and magnesium oxides, but derive from the specific ratio between the components, which is crucial in determining the buffer properties of the compound. In this respect, see the publication in J Pharmacol Exp Ther. 1992 December; 263(3): 1206-11 which demonstrates that compounds with different Al/Mg ratios have similar activities in vitro but different activities in vivo, where the aluminium ions tend to form complexes.